Geological Survey of Japan, Japan Petroleum Exploration Company, Teikoku Oil Company and other organs are vigorously carrying out exploration works of petroleum and natural gas through out the Kwanto Plain.
In this paper the writer makes clear the surface shape of the basement of Kwanto Plain through compiling gravimetric, seismic and well data which have been got by the above organs.
The writer shows Miocene paleogeography based on knowledges from overlying Miocene series, and he presents histrical views on the surface shape of the basement and his tectonic views on the structure of the basement.
He distinguished a Cenozoic (especially Tertiary) sinking trough, and concludes that the so-called Kwanto basin forming movement is one type of the sinking of the above mentioned Cenozoic sinking trough in a new phase.
